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linked_list.go
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linked_list.go
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package top_interview_questions_easy
import "strconv"
// ListNode describe LinkedList node.
type ListNode struct {
Val int
Next *ListNode
}
// deleteNode Problem: Delete Node in a Linked List.
//
// LeetCode: https://leetcode.com/explore/featured/card/top-interview-questions-easy/93/linked-list/553/
func deleteNode(node *ListNode) {
*node = *node.Next
}
// removeNthFromEnd Problem: Remove Nth Node From End of List.
//
// LeetCode: https://leetcode.com/explore/featured/card/top-interview-questions-easy/93/linked-list/603/
//
// Hint 1:
// Maintain two pointers and update one with a delay of n steps.
func removeNthFromEnd(head *ListNode, n int) *ListNode {
if head == nil {
return nil
}
if head.Next == nil && n == 1 {
return nil
}
last := head
elementToDelete := head
beforeLast := head
k := 0
for {
if k >= n {
elementToDelete = elementToDelete.Next
}
if last.Next != nil && last.Next.Next == nil {
beforeLast = last
}
if last.Next == nil {
break
}
last = last.Next
k++
}
if elementToDelete == head {
return elementToDelete.Next
}
if n == 1 && k == 1 {
head.Next = nil
return head
}
if elementToDelete == last {
beforeLast.Next = nil
return head
}
*elementToDelete = *elementToDelete.Next
return head
}
// reverseList Problem: Reverse Linked List.
//
// LeetCode: https://leetcode.com/explore/featured/card/top-interview-questions-easy/93/linked-list/560/
func reverseList(head *ListNode) *ListNode {
if head == nil || head.Next == nil {
return head
}
var prev *ListNode
// Go through whole list
for head.Next != nil {
next := head.Next // Save next
head.Next = prev // Set next to previous
prev = head // set new previous to current
head = next // set head to next
}
head.Next = prev // for last case set next to previous
return head
}
// mergeTwoLists Problem: Merge Two Sorted Lists.
//
// LeetCode: https://leetcode.com/explore/featured/card/top-interview-questions-easy/93/linked-list/771/
func mergeTwoLists(l1 *ListNode, l2 *ListNode) *ListNode {
if l1 == nil && l2 == nil {
return nil
} else if l2 == nil {
return l1
} else if l1 == nil {
return l2
}
if l1.Next == nil && l2.Next == nil {
if l1.Val > l2.Val {
l2.Next = l1
return l2
}
l1.Next = l2
return l1
}
first := 0
if l1.Val > l2.Val {
first = l2.Val - 1
} else {
first = l1.Val - 1
}
newHead := &ListNode{Val: first, Next: nil}
newList := newHead
for {
if l1 == nil && l2 == nil {
break
}
if l1 == nil {
tmp := *l2
tmp.Next = nil
l2 = l2.Next
newHead.Next = &tmp
newHead = newHead.Next
continue
}
if l2 == nil {
tmp := *l1
tmp.Next = nil
l1 = l1.Next
newHead.Next = &tmp
newHead = newHead.Next
continue
}
if l1.Val < l2.Val {
tmp := *l1
tmp.Next = nil
l1 = l1.Next
newHead.Next = &tmp
newHead = newHead.Next
continue
}
if l2.Val < l1.Val {
tmp := *l2
tmp.Next = nil
l2 = l2.Next
newHead.Next = &tmp
newHead = newHead.Next
continue
}
if l1.Val == l2.Val {
tmp := *l1
tmp.Next = nil
l1 = l1.Next
newHead.Next = &tmp
newHead = newHead.Next
tmp2 := *l2
tmp2.Next = nil
l2 = l2.Next
newHead.Next = &tmp2
newHead = newHead.Next
continue
}
}
return newList.Next
}
// isPalindromeList Problem: Palindrome Linked List.
//
// LeetCode: https://leetcode.com/explore/featured/card/top-interview-questions-easy/93/linked-list/772/
func isPalindromeList(head *ListNode) bool {
if head == nil || head.Next == nil {
return true
}
var s1, s2 string
for head != nil {
s1 += strconv.Itoa(head.Val)
s2 = strconv.Itoa(head.Val) + s2
head = head.Next
}
return s1 == s2
}
// hasCycle Problem: Linked List Cycle.
//
// LeetCode: https://leetcode.com/explore/featured/card/top-interview-questions-easy/93/linked-list/773/
func hasCycle(head *ListNode) bool {
if head == nil || head.Next == nil {
return false
}
existsMap := make(map[*ListNode]struct{})
for head.Next != nil {
if _, ok := existsMap[head]; ok {
return true
}
existsMap[head] = struct{}{}
head = head.Next
}
return false
}